Problems with Listview adapter

问题

I have an app which uses a Listview to display Lectures. The Lectures are colour coded according to their type. I used a custom adapter to control the different colours of each lecture. I call the adapter using the code below -

    cursor = myDbHelper.getReadableDatabase().rawQuery(sql, null);       
    startManagingCursor(cursor);
    adapter = new Lectures_Adapter(this,R.layout.menu_item,cursor,FROM,TO);        
    menuList.setAdapter(adapter);

This all works ok until I re-order the Lectures, say by Location. The code I use is -

    Cursor newCursor = myDbHelper.getReadableDatabase().rawQuery(sqlStr, null);
    adapter.changeCursor(newCursor);

The code in my custom adapter (Lectures_Adapter) is below but is not called when the Lectures are re-ordered.

     public class Lectures_Adapter extends SimpleCursorAdapter {
         private Context appContext;
         private int layout;
         private Cursor mycursor;

         public Lectures_Adapter(Context context, int layout, Cursor c, String[] from,int[] to) {
              super(context, layout, c, from, to);
              this.appContext=context;
              this.layout=layout;
              this.mycursor=c;               
         }

         @Override
         public View getView(int position, View convertView, ViewGroup parent)     
         {   
              View view = super.getView(position, convertView, parent);   
              try {             
                 if (position > 0)
                 {               
                    RelativeLayout rowFill = (RelativeLayout) convertView.findViewById(R.id.rowFill);
                    String title = mycursor.getString(1);                
                    int myColor = 0;
                    int myPos = title.indexOf("Nursing");
                    int myPos2 = title.indexOf("Masterclass");
                    if (myPos >= 0)
                    {
                        myColor = Color.parseColor("#99FF66");
                    }
                    else if (myPos2  >= 0)
                    {
                        myColor = Color.parseColor("#FF99FF");
                    }
                    else
                    {
                        myColor = Color.parseColor("#FFFF66");
                    }
                    convertView.findViewById(R.id.rowFill).setBackgroundColor(myColor);                 
                  }         
               }catch(Exception e) {

               }

              if (convertView == null) {
                  LayoutInflater inflator = (LayoutInflater) this.appContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                  convertView = inflator.inflate(this.layout,null);
              } else {
                  convertView = (View) convertView;
              }
              return view;  
          }

       }

Can somebody please tell me how I can re-order my Listview dynamically and call me custom adapter each time.

回答1:

The problem is that your code in getView() gets its data from the class variable mycursor, but when you call changeCursor, the mycursor variable is not getting updated, so you still see the original list. Rather than using mycursor, you should call getCursor() instead.

回答2:

Have you tried calling adapter.notifyDataSetChanged() after you call the changeCursor? That should force your menuList to be updated.

回答3:

Instead of using getView, you may want to use newView and bindView methods instead...here's an example from some code I've written.

private static class ViewHolder {
    HistoryRowView rowvw;
}

class ReportHistoryAdapter extends CursorAdapter {
    ViewHolder _holder;

    private static final String INFLATER_SVC = Context.LAYOUT_INFLATER_SERVICE;
    private LayoutInflater _inflater;

    public PostureReportAdapter( Context context, Cursor cursor ) {
        super( context, cursor );
        _inflater = (LayoutInflater) context.getSystemService(INFLATER_SVC);

    }

    @Override
    public View newView(Context context, Cursor cursor, ViewGroup parent) {
        View vw = _inflater.inflate( R.layout.reports_history_view, null );
        _holder = new ViewHolder();
        _holder.rowvw = (HistoryRowView)vw.findViewById( R.id.rhv_history_row_vw );
        vw.setTag( _holder );
        return vw;
    }

    @Override
    public void bindView(View vw, Context context, Cursor cursor) {
        _holder = (ViewHolder)vw.getTag();

        int poor = cursor.getInt( 0 );
        int fair = cursor.getInt( 1 );
        int good = cursor.getInt( 2 );
        int date = cursor.getInt( 3 );

        _holder.rowvw.setData( poor, fair, good, date );
    }
}

来源：https://stackoverflow.com/questions/9536848/problems-with-listview-adapter